2018-08-10

talking models; chemically identified tori

I gave my annual blackboard Königstuhl Colloquium today. This year I spoke about fitting models, which was a reprise of my 2010 talk that launched the infamous polemical tome. I spent some time on the point that you make your life hard (or your results wrong, or both) if you cut your data or select your sample on the quantities that your model generates. You should cut or trim or select on housekeeping data that aren't part of your probabilistic model! I also talked about outliers, model selection, and subjectiveness.

In the morning, I spent time talking with Rix (MPIA) and (by email) Jo Bovy (Toronto) about my chemical-tangents method, or the idea that dynamical tori must be tangent to chemical-abundance level surfaces in 6-d phase space. Bovy agreed with my position that this idea is new; though I wrote to him about it because it is so closely connected to things he has done and is doing. And Rix agreed that the method doesn't depend (to first order) on survey selection functions. He also made me a toy model that showed feasibility. So this project is on.